Some mechanisms of reduction of carotenoid levels in chickens infected with Eimeria acervulina or E. tenella.

The levels of plasma carotenoids were markedly reduced in broiler cockerels infected with Eimeria acervulina or E. tenella. The mechanisms of this depigmentation differed between the two species, being primarily associated with interference of absorption of xanthophyll (carotenoids) from the intestinal lumen with E. acervulina infection and with leakage through the damaged wall of the cecum with E. tenella infection. Chicks reared on an essentially carotenoid-free diet and inoculated with E. acervulina showed no detectable levels of carotenoids in the blood 48 hours after being changed to a diet containing 30 mg of xanthophyll/kg. Conversely, uninoculated chicks and chicks inoculated with E. tenella showed significant and similar increases in plasma levels of carotenoids. Chicks reared on a diet containing xanthophyll and inoculated with E. tenella showed a more rapid decrease in plasma carotenoids than did uninoculated controls when changed to a xanthophyll-free diet. In chicks fed high xanthophyll diets containing chromic oxide, no indication of malabsorption was seen in chicks infected with E. tenella compared with uninoculated controls, whereas chicks inoculated with E. acervulina showed significantly less xanthophyll absorption. Conversely, a marked increase in the xanthophyll : Cr2O3 ratio was observed in the cecal contents of chicks inoculated with E. tenella compared with uninuoculated controls or those inoculated with E. acervulina. Studies of uninoculated chicks pair-fed with chicks inoculated with E. acervulina or E. tenella indicated that the decrease in plasma carotenoids and increases in intestinal pH are not associated with the reduced intake of feed associated with infection. The studies involving uninoculated birds with reciprocal chagnes between high and low xanthophyll diets indicated that plasma carotenoids are a more rapid and sensitive means of measuring changes in pigmentation levels than are visual skin scores carotenoid levels from the skin.